#include <stdio.h>
#include <math.h>
#define ASIZE 13370

int main ()
{
	double x[ASIZE];
	double avg=0, deviat=0;
	int i=0, n;

	freopen("deviation.in", "r", stdin);
	freopen("deviation.out", "w", stdout);

	scanf("%d", &n);
	while (scanf("%lf", &x[i]) == 1 && i++ < n) {
		avg += x[i-1];
	}
	avg /= n;
	for (i = 0; i < n; i++)
		deviat += (x[i]-avg)*(x[i]-avg) / n;

	deviat = sqrt(deviat);
	printf("%lf\n", deviat);
	return 0;
}
